The simplest aryne, C6H4 (labeled 1 in the diagram to the right), is sometimes called benzyne. However, this name is open for criticism because it implies a triple bond which would be a special case of triple bonds, so a better name is didehydrobenzene. Benzyne is stabilized by resonance between structures 1 and 2—a better representation of the electronic structure is 3. The "extra" pi bond (4b) is localised and orthogonal to the other pi bonds making up the aromatic ring (4a). Benzyne can also be drawn as a diradical: the pi bond 4b splits homolytically, leaving one electron on each of the two atoms that are formally part of that bond.
Benzyne is an extremely reactive species due to the nature of its triple bond. In normal acetylenic species (such as the simplest, ethyne) the unhybridized p orbitals are parallel to one another above and below the molecular axis. This facilitates maximum orbital overlap. In benzyne, however, the p orbtials are distorted to accommodate the triple bond within the ring system, reducing their effective overlap. A suitable chemical trap for benzyne is a cyclopentadiene.
There are three possible diradical didehydrobenzenes: 1,2-didehydrobenzene, 1,3-didehydrobenzene and 1,4-didehydrobenzene. Their energies in silico are respectively 106, 122, and 138 kcal/mol (444, 510, and 577 kJ/mol). The 1,4-diradical species has been identified in the Bergman cyclization. Professor Maitland Jones of Princeton University has studied the interconversion of the 1,2-, 1,3- and 1,4-didehydrobenzenes.
Anthracene is converted to a triptycene by Diels-Alder reaction of an aryne with the central benzene ring . A pentiptycene is the anthracene analogue after the reaction with 1,2,4,5-tetrabromobenzene and butyllithium.
Aryne reactivity can also be extended to carbon insertion reactions into substrates that can react both as a nucleophile and as an electrophile with for instance a malonic acid ester . The precursor of benzyne in this reaction is 2-(trimethylsilyl)phenyl triflate.
This reaction takes place through several reactive intermediates: the aryne 2 is formed from phenyl substituted phthalic anhydride which rearranges with ring contraction to the vinylidene 3. This carbene gives a C-H insertion reaction to pentalene 4 and then an extrusion to vinylidene 5. After cis-trans isomerisation to 6 a final insertion reaction gives the acenaphthylene. Evidence for a phenyl migration in aryne 2 from the 1,2-didehydrobenzene to the 1,3-didehydrobenzene is based on isotope scrambling. When the ipso carbon atom is replaced by 13C in the precursor molecule it will in the default mechanism again show up in the acenaphthylene in an ipso arene position. The presence of 13C in the bridge position can only be explained when 15% of 2 isomerizes to 1,3-didehydrobenzene A.